The present invention relates to a respiratory hose made of translucent or transparent rubber-elastic material having along its outer periphery a helical rib bar; also the hose is to be heated by means of an electrical conductor.
Respiration hoses of the kind to which the invention are used for example as emergency equipment to feed breathing air to a patient possibly at the site of an accident or while moving the patient to a hospital. These hoses are transparent or translucent in order to permit visual monitoring of the hose, e.g. whether or not it is plugged. The ribs or bars prevent the hose from being squeezed shut in the case of bending; i.e. these bars, etc., serve as protection.
Since the conditions of employment are often unforeseeable certain adverse weather conditions have to be taken in consideration. For instance, in a cold temperature, the outer surface of the hose may be very cold, but the hot air passing through the hose contains moisture that may readily precipitate in the hose and then be sucked in by the patient.
European Patent EP 0 214 976 31 suggests the heating of the respiration air by placing a heating wire in the inner wall of an otherwise smooth wall tube. The heating wire is loosely placed. Such a synthetic hose does not guarantee unimpeded function when bent. Moreover, the heater warms the passing air and not the hose wall. Thus, the air in the tube is cooled and precipitation and condensation of water are not avoided. In order to remedy this situation it has been suggested to insert the heating wire spirally in the hose wall. In such a case, however, the heat distribution is no longer uniform. Moreover, the arrangement of the heating wire in the spirals of the hose requires bridging the large distance to the interior of the hose. Furthermore, a considerable amount of heat is lost to the outside air owing to the fact that the spirals extend from the hose surface. The totality of heat does not contribute to the main task, namely, heating the air in the hose.